I honestly don't think we'll see any drastic changes for a while, given that they're still trying to get CT finished, and the number of new subscriptions seems to growing exponentially. Now, if all these noobs bag it after a few months, something might change, but for the sake of discussion-
Abolish combined ranking for all the arenas. I'd be happy with just stats, but it might discourage some of the scorepadding in the empty arenas, and take away incentive for the vulching hordemonkeys.
No kill messages upon landing.
Reset player perks at some interval. Now, things that require perks- additional drones, perked ordnance, perk multipliers, etc gain some limited relevance that they are now lacking for the vets.
Make ENY hurt. All sorts of ways to do that.
Home arenas. Give players the opportunity to declare a home arena for their squad. It would probably be prohibitively time consuming for HTC to shuffle open spots around, but perhaps it could be coaded in such a way as to evenly distribute groups. I recall seeing a remark by HiTech that they expected people to find "their" arena, and that numbers were expected to eventually level out. Neither has really happened, so why not just let squads fly together, and use ENY, perk mults, and some other thing to offset the numbers issues. As an example, no perk rides, no large bombs, and a more aggressive ENY limit for the side with numbers.
Make the arenas entirely separate. Same maps, same basic setups, but no more side switching timer tying the 2, no common scoring, maybe even separate squads.
No joining a country with higher numbers. Want to fly together in blue? Change sides. Higher perk rewards, higher eny penalties, and a guarantee to fly with your entire squad somewhere. If you insist on loyalty to chess piece Y instead of X, well, no squad for you.
There's probably issues with every idea, and part of what is enjoyable about the game is the lack of heavy structure, but the same lack of structure results in things happening which can't be good for gameplay or customer retention, especially with so many newer players, and maybe some guidelines for what's allowable, or different rewards/penalties could improve things. Any change whatsoever will result in massive whining, but maybe something positive could come from all of this.